The present invention relates to an attachment for a sugar cane grab loader formed of two mechanical arms that move the tips of the grab's tines parallel to surface of the ground during closing of the grab, avoiding introduction of soil and other extraneous materials during cane loading.
A known type of mechanical sugar cane loader uses a pushpiler for bundling the cane over the soil and a mechanical grab suspended from a boom of the pushpiler for raising the cane and loading it on trucks. A major problem in the operation of such mechanical sugar cane loaders, is that a significant amount of soil and other extraneous materials is collected with the sugar cane, as well as the destruction of stubs, by the action of the grab and the pushpiler penetrating the ground.
A conventional grab is generally formed of two curved elements articulated at the point of their suspension from the boom. During the closing movement, the grab's tips trace a circular path around the point of their suspension at the boom and they tend to penetrate the soil if the position of elevation of the boom remains constant. To avoid penetration into the ground of the tips of a conventional grab, an operator has to lift the boom simultaneously with closing of the grab. This is very difficult and not very exact. In reality, it is not possible for the operator to avoid at least a partial ground penetration during the alternative action of two hydraulic cylinders, and neither can he avoid leaving some amount of cane on the ground, if the boom rises too quickly. In the case of any cane left on the field, the operator must bundle it again with a pushpiler, spending additional time, and incorporating more undesirable soil with the cane.
Many efforts have been made to avoid soil penetration by the tips of a conventional grab during its closing movement. Some of them consist of a modification to the shape of the grab (South African Patent RSA-807616) or the separation of the articulation points of each grab's elements, but it was still impossible to avoid ground penetration.
The most interesting attempt to solve this problem is shown in U.S. Pat. No. 4,614,476 wherein an auxiliary hydraulic cylinder is connected with the grab and the boom actuating cylinders in such a manner that the actuating pressure of the grab cylinder or the hydraulic fluid expelled during the closing movement of the grab, actuates the auxiliary hydraulic cylinder which at the same time activates the boom cylinders to automatically raise the grab to the desired elevation. Another alternative of the same patentee consists of the use of a servovalve at the boom or at the boom support. When the valve is actuated at the lowest position of the boom, the closing movement of the grab is accompanied by a rising of the boom due to the servohydraulic action between the grab's hydraulic cylinders and the boom. However, the hydraulic interaction between the grab's cylinders and the boom does not guarantee a path of the grab's tips along the surface. Besides, it necessitates an important additional cost to the machine. Considering also a change of the volumetric efficiency of the elements of the hydraulic system used in the machine, the hydraulic interaction between the grab's cylinders and the boom's can vary, thus changing the path of the grab's tips. Accordingly, this alternative does not provide good results when a grab with two hydraulic cylinders is used, such is the situation with many sugar cane loaders.
The present invention has overcome the inconveniences mentioned above with a new and improved mechanical system for fastening a sugar cane grab loader to the boom of a pushpiler.